Electric-arc lamp.



No. 653,572. Patanted July 10, I900. J. A. FLEMING.

ELECTRIC ARC LAMP.

(Application filed. Dec. 28, 1899.)

odel.

UNITED STATES PATENT OFFICE.

JOHN AMBROSE FLEMING, OF LONDON, ENGLAND.

ELECTRIC-ARC LAMP.

SPECIFICATION forming part of Letters Patent No. 653,572, dated. July 10, 1900. Application filed December 23, 1899. Serial No. 741,402. (No model.)

To all whom it Wwty concern: 7

Be it known that I, JOHN AMBROSE FLEM- ING, doctor of science and professor of electrical engineering, a citizen of England, residing at University College, Gower street, London, England, have invented a certain new and useful Improvement in Electric-Arc Lamps, (for which I have made application for a patent in Great Britain, dated June 2,

1899, No. 11,506, and in Germany, dated July 25, 1899, F. 12,O9l /2lf. of which the following is a specification.

It has been proposed to make the carbon of an electric lamp with an internal core or an external sleeve of some material, such as a refractory oxid, which when heated by the are produced on first putting the lamp in circuit should become so far conductive that the circuit instead of forming an are between the carbons should pass through this core or sleeve, heating it to incandescence, the lamp being no longer of the are kind, but of the glow kind.

My invention relates to the application of refractory cores or rods of'special kind to the carbons of an electric-arc lamp in such a manner that they instead of becoming heated, so as to become conductive by the passage of current through them, and then becoming further heated, so as to glow, are heated by the are itself, which is maintained between the carbons, and by their brilliant incandescence largely increase the illuminating power of the lamp. For this purpose I make and arrange the carbons as I shall describe, referring to the accompanying drawings.

Figure 1 is a side View, partly sectional, showing an arrangement of the carbons of a lamp according to my invention. Figs. 2 and 3 are plans of the two carbons, respectively.

I make the one carbon CL with two parallel holes or bores 1) extending along it, and into these bores I place looselycores which-are conveniently made in separate pieces 0 in the following manner; I subject pure dry magnesia to great endwise pressure in a tubular mold, and thus form it into astick or penoil, which I then heat to the highest attainable temperature in an electric furnace. The pencils thus prepared are exceedingly hard and of high electrical resistance. They are made ofsuch diameter that they can slide quite freely in the bores of the carbon, so that when this carbon is vertical or not much inclined from the vertical they can slide down by gravity and lodge on the lower carbon. When the carbon thus cored is horizontal or so far inclined that the cores cannot descend by gravity, they may be urged forward by springs or otherwise, so as to bear always against the other carbon. The carbon a, as well as the other carbon (1, is preferably made of section having straight sides and ends rounded, as indicated by the dotted arcs in Fig. 2,'so that these ends in the act of molding the upper carbons are sufficiently strong to be cored; but after the carbons are baked the rounded edges are to a great extent ground 0E, leaving only a very thin wall of carbon outside the refractory cores. The lower carbon is made of the same sectional form as the upper carbon, but without the bores.

The carbons being fed and regulated by any of the known arrangements for that purpose employed in arc-lamps, the operation is as follows: When the lamp is out of circuit, the carbons are in contact, and when it is put in circuit the regulating apparatus separates the carbons, striking the arc, but leaving the two cores'of the one carbon bearing against the other carbon. The are, which is formed mostly in the space between the two cores and remains steadily in that position, heats.

the cores to brilliant incandescence. The feeding and regulation of the carbons go on in the usual way, the two cores remaining in position, and as they gradually waste away fresh lengths of them are protruded from the bores of a, so as always to bear on the end of (Z, however the carbons-themselves are moved or consumed.

Owing to the very small body of carbon outside the refractory cores, the arc remains almost constantly in the middle between those rods, for the moment it strays toward either side the thin wall of carbon is at once con= sumed,causing the arc to return to the middle.

Having thus described the nature of this invention and the best means I-know of carry ing the same into practical effect, I claim An electric-arc lamp employing two carbons one of which is provided with two longitudinal bores separated from each other to leave an intermediate carbon-wall, and a core or rod of refractory material freely arranged my hand in presence of two subscribing witin each of said bores and presenting themnesses.

selves to the opposite carbon in such manner 7 that the electric arc Will be formed between I JOHN, AMBROSE FLEMING 5 said cores or rods and thus heat them to in- Witnesses:

candeseence, substantially as described. FRED O. HARRIS,

In testimony whereof I have hereunto set GERALD L. SMITH. 

